biogenesis of stress-induced tRNA-derived RNAs

Stress-induced tRNA-derived RNAs (tiRNAs), found in diverse eukaryotes, generated by endonucleolytic cleavage in the anticodon loop of mature tRNAs, catalyzed by Rny1 in yeast [PMID: 19332891]. Under normal conditions Rny1 is sequestered in the vacuole away from its substrates [PMID: 19332891].

Rny1 is an RNase T2 family member, and is predicted to leave 5' hydroxyl and 2' -3' cyclic phosphate groups. This is unusual for intracellular cleavage and significant because the 5' hydroxyl group confers resistance to degradation by the 5' exonucleases Xrn1 and Rat1/Xrn2. Moreover, the tRNAsplicing ligase requires 5' hydroxyl and 2' -3' cyclic phosphate groups, suggesting that tRNA anticodon cleavage might be reversible under some circumstances.